||25% blast furnace slag or |
10% cenospheres or
0-40% fly ash or
5% silica fume
||Each region of the country will be different concerning availability of concrete/cement with these additives, dependent on the respective industries in the region--be it fly ash from coal-fired power plants, cenospheres from fly ash, silica fume from electric arc furnace stacks, etc. Cement in small quantities (bags) is not generally available with these additives. |
Bagged cement with recycled content is also available. Two brands that contain recycled content are Basalite and Quikrete IF produced in an area where the specified recycled material is available. Quikrete is developing a map to denote if we purchase bags of Quikrete in areas a, b, c we know they contain fly ash and can claim credit for that purchase. If we purchase bags of Quikrete in areas x, y, z we know they do not contain fly ash and should then denote those purchases not available. To date the Quikrete production areas we know are producing bags of cement with fly ash are Fremont, CA; Charlotte, NC; Nashville, TN; Pounding Mill, VA; and Martinsville, VA. In addition, Quikrete has a "Green Concrete Mix" which contains 50% or more recycled aggregate such as recycled concrete. Basalite production codes that denote fly ash and/or blast furnace slag is in the product begin either with 1406 or 1409. The production codes are printed on the bag in front of the date. A third brand (FA-S10, FA-S-6, MS-S10, MS-S6) contains either fly ash (the FA brand) or silica fume (the MS brand). However, this brand is sold in bagged form only in the Chicago area.
||Price for concrete/cement with the additives is typically similar to the price without the additives. Should that not be the case in your region, please let us know.|
The additives not only make use of a material that would otherwise be wasted but they increase the strength, endurance, thermal stability (in the case of cenospheres), electrical resistivity (in the case of silica fume) of concrete and decrease shrinkage and weight (in the case of cenospheres) and fluid permeability (in the case of silica fume), thereby reducing damage from thaw/freeze cycles.
The additives do increase curing time and so a lower percent of the additive should be requested when pouring concrete in cold temperatures.
||Cast-in-Place Concrete (Spec 03300) |
Pertinent Language from Sandia National Lab
B. American Society for Testing and Materials (ASTM)
C618 Specification for Fly Ash and Raw or Calcined
Natural Pozzolan for Use as a Mineral Admixture
in Portland Cement Concrete
2.04 CONCRETE MATERIALS
A. Portland Cement: ASTM C150 Types I-II and III, "Low-Alkali"
cement, unless otherwise specified. Use one brand of cement
throughout project unless otherwise acceptable to the SDR
D. Fly Ash: ASTM C618, Class F; use one brand of fly ash
throughout project unless otherwise acceptable to the
2.06 CONCRETE MIX DESIGN
4. Fly Ash: Fly ash shall be used in all concrete mixes.
Class F fly ash shall be proportioned by weight of
cement to provide fly ash to Portland cement ratio not
less than 20%, or greater than 25% of the sum of total
weight of fly ash and cement.
||Concerns have been expressed about hazardous materials leaching out of concrete with additives. The fly ash used in concrete is a byproduct from coal fired power plants, for example, and not a hazardous waste. Fly ash from municipal solid waste combustors would be a hazardous waste, but that is not the fly ash used in concrete.|
||According to the Western Region Ash Group, each ton of fly ash used to replace a ton of cement saves the equivalent of one barrel of oil required to produce the cement. See the King County "Fly Ash in Concrete" bulletin for more information. |
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